Allocating transmit power among multiple air interfaces

ABSTRACT

Systems and methods for allocating transmit power among multiple interfaces in a wireless communication system are disclosed. In one embodiment, the method comprises determining a first power level that is used for transmitting over a first air interface, determining a maximum power level available for transmitting over a second interface, comparing the first power level to the maximum power level, determining a second power level that is used for transmitting over the second air interface based on the comparison of the first power level to the maximum power level, and generating a power-based payload constraint based on the second power level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under §119(e) to the following U.S.Provisional Applications: (1) U.S. Prov. App. No. 61/178,332, entitled“System and method for resolving conflicts between air interfaces in awireless communication system,” filed May 14, 2009; (2) U.S. Prov. App.No. 61/178,452, entitled “Allocating transmit power among multiple airinterfaces,” filed May 14, 2009; and (3) U.S. Prov. Appl. No.61/178,338, entitled “System and method for dropping and adding an airinterface in a wireless communication system,” filed May 14, 2009. Theabove-referenced applications are herein incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to communication networks and systems.In particular, the invention relates to systems and methods forallocating power among multiple air interfaces for a mobile devicesupporting simultaneous transmission using multiple air interfaces.

2. Description of the Related Art

Many forms of wireless communication systems and networks are used totransmit various forms of data including, but not limited to, voice,video, multimedia, and packet data. In some cases a mobile device thatcommunicates on such a network supports transmission over multiple airinterfaces (e.g., 1x, 1xAdvanced, DO, UMTS (HSPA+), GSM, GPRS, EDGE,etc.). In the related art, mobile devices only transmit over one airinterface at a time. Therefore, power allocation in the related art onlydeals with allocating power to a single air interface at a time.Therefore, the related art does not describe power allocation betweenmultiple air interfaces where a mobile device transmits on multiple airinterfaces simultaneously. Thus, it is desirable to provide an efficientpower allocation strategy for mobile devices that transmit on multipleair interfaces simultaneously.

SUMMARY OF THE INVENTION

The systems, methods, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, its more prominent features will now bediscussed briefly. After considering this discussion, and particularlyafter reading the section entitled “Detailed Description of CertainEmbodiments” one will understand how the features of this inventionprovide advantages that include concurrent communication over multipleair interfaces.

One aspect of the disclosure is a method for allocating power amongmultiple air interfaces for a communication device supportingsimultaneous transmission over multiple air interfaces, the methodcomprising determining a first power level that is used for transmittingover a first air interface, determining a second power level availablefor transmitting over a second interface, comparing the first powerlevel to the second power level available for transmitting over a secondinterface, determining an estimated second power level for transmittingover the second air interface based on the comparison of the first powerlevel to the second power level, and generating a power-based payloadconstraint based on at least the estimated second power level.

Another aspect of the disclosure is a wireless communication devicesupporting simultaneous transmission on multiple air interfaces, thewireless communication device comprising a first interface power levelcalculator configured to determine a first power level that is used fortransmitting over a first air interface, a second interface power levelcalculator configured to determine a second power level available fortransmitting over a second interface, a differential check unitconfigured to compare the first power level to the second power levelavailable for transmitting over a second interface, a second interfacepower level adjuster configured to determine an estimated second powerlevel for transmitting over the second air interface based on thecomparison of the first power level to the second power level, and apower-based payload constraint calculator configured to generate apower-based payload constraint based on at least the estimated secondpower level.

Another aspect of the disclosure is a system for allocating power amongmultiple air interfaces for a communication device supportingsimultaneous transmission over multiple air interfaces, the systemcomprising means for determining a first power level that is used fortransmitting over a first air interface, means for determining a secondpower level available for transmitting over a second interface, meansfor comparing the first power level to the second power level availablefor transmitting over a second interface, means for determining anestimated second power level for transmitting over the second airinterface based on the comparison of the first power level to the secondpower level, and means for generating a power-based payload constraintbased on at least the estimated second power level.

Another aspect of the disclosure is a computer program product,comprising, computer-readable medium comprising code for causing acomputer to determine a first power level that is used for transmittingover a first air interface, code for causing a computer to determine asecond power level available for transmitting over a second interface,code for causing a computer to compare the first power level to thesecond power level available for transmitting over a second interface,code for causing a computer to determine an estimated second power levelfor transmitting over the second air interface based on the comparisonof the first power level to the second power level, and code for causinga computer to generate a power-based payload constraint based on atleast the estimated second power level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating wireless communication devices engagedin simultaneous communication over two air interfaces.

FIG. 2 is a functional block diagram of a wireless communication device.

FIG. 3 is a functional block diagram of a receiver of a wirelesscommunication device.

FIG. 4 is a functional block diagram of a transmitter of a wirelesscommunication device.

FIG. 5 illustrates one embodiment of a functional block diagram of awireless communication device.

FIG. 6 illustrates the input and output of one embodiment of apower-based payload constraint calculator.

FIG. 7 illustrates a flowchart of a process of calculating a power-basedpayload constraint.

FIG. 8 illustrates a flowchart of a process of adjusting the powermargin using a margin loop.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The techniques described herein may be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDM, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). Long TermEvolution (LTE) is an upcoming release of UMTS that uses E-UTRA. UTRA,E-UTRA, GSM, UMTS and LTE are described in documents from anorganization named “3rd Generation Partnership Project” (3GPP). cdma2000is described in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). These various radio technologies andstandards are known in the art.

Single carrier frequency division multiple access (SC-FDMA), whichutilizes single carrier modulation and frequency domain equalization isa technique. SC-FDMA has similar performance and essentially the sameoverall complexity as those of OFDMA system. SC-FDMA signal has lowerpeak-to-average power ratio (PAPR) because of its inherent singlecarrier structure. SC-FDMA has drawn great attention, especially in theuplink communications where lower PAPR greatly benefits the mobileterminal in terms of transmit power efficiency. It is currently aworking assumption for uplink multiple access scheme in 3GPP Long TermEvolution (LTE), or Evolved UTRA.

Methods and devices described herein are related to allocating transmitpower among multiple air interfaces at a wireless communication device.The described embodiments are related to wireless communication devicesthat transmit over two air interfaces. However, one of ordinary skill inthe art will recognize that similar methods and devices may be used tosupport transmission over more than two air interfaces.

Some embodiments of wireless communication devices described herein areconfigured to transmit over multiple air interfaces simultaneously. Eachair interface may correspond to a different communication standard.Accordingly co-channels or channels using a single communicationstandard do not correspond to different air interfaces. For example, awireless communication device may communicate voice over a first airinterface (e.g., 1x) and data only over a second air interface (e.g.,DO). Transmitting the voice over the first interface may require thevoice signal be amplified to a first power level. The first power levelmay be chosen in order to maintain a certain level of voice quality. Ahigher power level may correspond to a stronger signal sent by thewireless communication device. The stronger signal may be lesssusceptible to errors and therefore results in a higher quality receivedvoice signal (e.g., less noise).

Further, transmitting data over the second interface may require thedata signal be amplified to a second power level. The second power levelmay be chosen in order to maintain a certain transmission data rate. Ahigher power level may correspond to a stronger signal sent by thewireless communication device. The stronger signal may be lesssusceptible to errors and therefore more data and less error-correctingbits may be sent over the communication channel.

Accordingly, higher transmit power levels for each air interface may bebeneficial. However, the wireless communication device may beconstrained to an overall power level available for transmission overboth the first and second air interfaces. The overall power level may beconstrained by factors such as interference between the air interfacesand/or other devices and minimization of battery power consumption.Accordingly, methods and devices for allocating the overall power levelbetween multiple air interfaces are described below. The overall powerlevel available may be a static constraint or may change dynamically.

Transmission over the multiple air interfaces may be divided into framesor subframes. Accordingly, in some embodiments the methods describedherein may be used to allocate power between multiple air interfaces foreach frame or subframe individually. In other embodiments, the methodsmay be used to allocate power for multiple frames or subframes.

FIG. 1 is a diagram illustrating wireless communication devices engagedin simultaneous communication over two air interfaces. Each wirelesscommunication device 10 can simultaneously establish a first airinterface 110 and a second air interface 120 between itself and anaccess point 130. In one embodiment, the first air interface 110 isestablished at a first channel defined by a first frequency or frequencyband, whereas the second air interface 120 is established at a secondchannel defined by a second frequency or frequency band which isdifferent from the first frequency or frequency band. In one embodiment,the first air interface 110 and the second air interface 120 are bothestablished with the same access point 130. In another embodiment, thefirst air interface 110 and the second air interface 120 are eachestablished with a different access point 130. Each of the access points130 may be located in a different geographical location. Further, in oneembodiment control of the two air interfaces is done completely at thewireless communication device 10. Accordingly, there is no interactionbetween the air interfaces at the access point 130. The lack ofinteraction at the access points 130 means that the access points 130 donot control one air interface based on metric of another air interface.In yet another embodiment, the only control that the wirelesscommunication device 10 exerts over one air interface based on anotherair interface is power level control based which may be based onperformance metrics of each air interface.

In some embodiments, the wireless communication device 10 may have anaccess state and a traffic state for each air interface 110 and 120.When a given air interface 110 or 120 is in an access state, thewireless communication device 10 does not actively transmit or receivedata over the given air interface 110 or 120. In the access state, thewireless device 10 may wait for a message. Upon receiving the messagefrom either an external device or internally, the wireless communicationdevice 10 air interface 110 or 120 may enter a traffic state. In atraffic state, the wireless communication device 10 actively transmitsor receives data over the given air interface device 110 or 120.

In one embodiment, the first air interface 110 supports 1xRTT trafficand the second air interface 120 supports EVDO traffic. 1xRTT, alsoknown as 1x, 1xRTT, and IS-2000, is an abbreviation of 1 times RadioTransmission Technology. EVDO, abbreviated as EV or DO, is anabbreviation of Evolution-Data Only. Both 1xRTT and EVDO aretelecommunications standards for the wireless transmission of datathrough radio signals maintained by 3GPP2 (3^(rd) Generation PartnershipProject), which are considered types of CDMA2000 (Code Division MultipleAccess 2000).

In other embodiments, the first air interface 110 or the second airinterface 120 can support 1xAdvanced, DO (Release 0, Revision A or B),UMTS (HSPA+), GSM, GPRS, and EDGE technologies.

FIG. 2 is a functional block diagram of a wireless communication device.The wireless communication device 10 includes a processor 210 in datacommunication with a memory 220, an input device 230, and an outputdevice 240. The processor is further in data communication with a modem250 and a transceiver 260. The transceiver 260 is also in datacommunication with the modem 250 and an antenna 270. Although describedseparately, it is to be appreciated that functional blocks describedwith respect to the wireless communication device 10 need not beseparate structural elements. For example, the processor 210 and memory220 may be embodied in a single chip. Similarly, two or more of theprocessor 210, modem 250, and transceiver 260 may be embodied in asingle chip.

The processor 210 can be a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anysuitable combination thereof designed to perform the functions describedherein. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The processor 210 can be coupled, via one or more buses, to readinformation from or write information to memory 220. The processor mayadditionally, or in the alternative, contain memory, such as processorregisters. The memory 220 can include processor cache, including amulti-level hierarchical cache in which different levels have differentcapacities and access speeds. The memory 220 can also include randomaccess memory (RAM), other volatile storage devices, or non-volatilestorage devices. The storage can include hard drives, optical discs,such as compact discs (CDs) or digital video discs (DVDs), flash memory,floppy discs, magnetic tape, and Zip drives.

The processor 210 is also coupled to an input device 230 and an outputdevice 240 for, respectively, receiving input from and providing outputto, a user of the wireless communication device 10. Suitable inputdevices include, but are not limited to, a keyboard, buttons, keys,switches, a pointing device, a mouse, a joystick, a remote control, aninfrared detector, a video camera (possibly coupled with videoprocessing software to, e.g., detect hand gestures or facial gestures),a motion detector, or a microphone (possibly coupled to audio processingsoftware to, e.g., detect voice commands). Suitable output devicesinclude, but are not limited to, visual output devices, includingdisplays and printers, audio output devices, including speakers,headphones, earphones, and alarms, and haptic output devices, includingforce-feedback game controllers and vibrating devices.

The processor 210 is further coupled to a modem 250 and a transceiver260. The modem 250 and transceiver 260 prepare data generated by theprocessor 210 for wireless transmission via the antenna 270 according toone or more air interface standards. The modem 250 and transceiver 260also demodulate data received via the antenna 270 according to one ormore air interface standards. The transceiver can include a transmitter,receiver, or both. In other embodiments, the transmitter and receiverare two separate components. The modem 250 and transceiver 260, can beembodied as a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anysuitable combination thereof designed to perform the functions describedherein.

FIG. 3 is a functional block diagram of a receiver of a wirelesscommunication device. A signal received on the antenna 270 is amplifiedby a low-noise amplifier 310. Depending on the particular embodiment,the amplified signal then passes through a SAW (surface acoustic wave)filter 320. A SAW filter is an electromechanical device in whichelectrical signals are converted into a mechanical wave in a deviceconstructed of a piezoelectric crystal or ceramic. The mechanical waveis delayed as it propagates across the device before being convertedback into an electric signal by electrodes. The delayed outputs arerecombined to produce a direct analog implementation of a finite impulseresponse filter. The signal is then multiplied by a center frequency ata multiplier 330. The base-banded signal is then passed through ananalog low-pass filter 340, converted to a digital signal at ananalog-to-digital converter 350, and filtered once again with a digitallow-pass filter 360.

The signal is then split into multiple paths. Each path is multiplied bya different frequency at a multiplier 370 and passed through anappropriate filter 380 before being sampled with a sampler 390. Furtherprocessing, including demodulation, equalization, deinterleaving, anderror correction coding, can be performed in a processing module 395 orthe modem 250 or processor 210 of FIG. 2.

FIG. 4 is a functional block diagram of a transmitter of a wirelesscommunication device. The function of the transmitter is similar to thatof the receiver, but in reverse. In particular, data generated by theprocessor 210 of FIG. 2 may be subject to preliminary processing in aprocessing module 495, the modem 250, or the processor 210 itself. Thedata for each channel is passed through an appropriate filter 480 beforebeing modulated at a multiplier 470. The modulated carriers are addedtogether at an adder 455 before being converted into an analog signal ata digital-to-analog converter 450. The analog signal is passed throughan analog low-pass filter 440 before being modulated to a centerfrequency at a multiplier 430. The modulated signal is optionally passedthrough a SAW filter 420 and a power amplifier 410 before beingtransmitted via the antenna 270.

FIG. 5 illustrates one embodiment of a functional block diagram of awireless communication device. In some embodiments, the various blocksmay be implemented as software and/or firmware. The wirelesscommunication device 500 includes a first interface power levelcalculator 502. In one embodiment, the first interface power levelcalculator calculates a first power level chosen for transmitting overthe first air interface. Wireless communication device 500 may alsoinclude a second interface power level calculator 504 configured tocalculate a maximum available power level for transmitting over thesecond air interface (e.g., the total power for transmitting over bothair interfaces (which may be a static or dynamic constraint) minus thepower used to transmit over the first air interface). Both firstinterface power level calculator 502 and second interface powercalculator 504 may be in data communication with differential check unit506. Differential check unit 506 may determine whether the maximumavailable power level for transmitting over the second interface differsfrom the first interface power level for transmitting over the firstinterface by a power differential threshold. The power differentialthreshold may be static or dynamically configured.

Accordingly, in one embodiment differential check unit 506 may firstdetermine the difference between the maximum available power level fortransmitting over the second interface and the first interface powerlevel. Differential check unit 506 may then compare the calculateddifference to the power differential threshold. If the calculateddifference is greater than the threshold, the differential check unit506 may signal a second interface power level adjuster 508 to determinea transmit power for the second air interface as discussed with respectto FIG. 7. If the calculated difference is less than the threshold, thedifferential check unit 506 may signal the second interface power leveladjuster 508 to set the transmit power for the second air interface tothe maximum available power level for transmitting over the secondinterface as discussed with respect to FIG. 7. In some embodiments, thetransmit power differential between the first air interface and thesecond air interface may be controlled to an acceptable level. Theactual level may depend on the specific RF implementation of each airinterface. Differential check unit 506 may be in data communication withsecond interface power level adjuster 508. Second power level adjuster508 may estimate a power level for transmitting over the second airinterface as discussed with respect to FIG. 7.

Second power level adjuster 508 may be in data communication withpower-based payload constraint calculator 510. Power-based payloadconstraint calculator 510 may generate a power-based payload constraint(e.g., power allocation (PA) headroom) based on certain factorsdescribed below. The power-based payload constraint calculator 510 maybe in data communication with processor 512 and transceiver 518.Processor 512 may be in data communication with memory 514 and powercontroller/amplifier 516. Power controller/amplifier 516 may be in datacommunication with transceiver 518. In some embodiments, processor 512may be similar to processor 210, memory 514 may be similar to memory220, and transceiver 518 may be similar to transceiver 260. Powercontroller/amplifier 516 may allocate power levels to each airinterface.

It should be noted that other embodiments of a wireless communicationdevice may include additional modules or may not include all of themodules shown in FIG. 5.

FIG. 6 further illustrates the input and output of one embodiment thepower-based payload constraint calculator of FIG. 5. Power-based payloadconstraint calculator 614 may generate a power-based payload constraintaccording to methods described with respect to FIG. 7. Power-basedpayload constraint calculator 614 may take in one or more inputs. Forexample, power-based payload constraint calculator 614 may receive asinput a first transmit power, which corresponds to the transmit powerlevel chosen for the first air interface. Power-based payload constraintcalculator 614 may also receive as input a second transmit pilot power(e.g., peak pilot or instantaneous pilot), which corresponds to thepower required to transmit a pilot of a carrier of the second airinterface. In addition, power-based payload constraint calculator 614may receive as input an estimated second transmit power for transmittingover the second air interface. Further, power-based payload constraintcalculator 614 may receive as input a power margin corresponding to acalculated margin for transmitting the pilot of the carrier of thesecond air interface. In some embodiments, the power margin may be afixed value. In other embodiments, the power margin may be adjusted. Onesuch embodiment is described with respect to FIG. 8. An overhead gainmay also be input into power-based payload constraint calculator 614,wherein the overhead gain is the required overhead power to transmit thepilot of the carrier of the second air interface. Based on one or moreinputs, power-based payload constraint calculator 614 may calculate apower-based payload constraint that is used to allocate power betweenmultiple air interfaces. It should be noted that other inputs may beinput into power-based payload constraint calculator 614 that aresimilar to the inputs described in order to calculate the power-basedpayload constraint.

FIG. 7 illustrates a flowchart of a process 700 of calculating apower-based payload constraint and using the power-based payloadconstraint to allocate power. In some embodiments, the steps of process700 may be performed by various components of wireless communicationdevice 500. The following description is just one embodiment of process700 described with respect to one embodiment of wireless communicationdevice 500. It should be noted that process 700 may be performed byother wireless communication devices and the steps of process 700 may beperformed by components other than those described below.

At a step 702, first interface power level calculator 502 determines thefirst power level chosen for transmitting over the first air interface.In some embodiments, the power level chosen for transmitting over thefirst air interface may be the power level at which transmission isalready occurring over the first air interface. In some suchembodiments, the chosen power level for transmitting over the first airinterface may be retrieved from memory 512. The first interface powerlevel calculator 502 may also apply an IIR filter (e.g., 1-tap IIRfilter with a selected time constraint (e.g., 1 frame)) to the retrievedpower level. The filter may be set based on a mode of the first airinterface (e.g., 1xAdvanced mode of the 1x air interface). The filtermay be reset when the first air interface leaves the traffic state.

Further at a step 704, second interface power level calculator 504calculates a maximum available power level for transmitting over thesecond air interface. In one embodiment, the maximum available powerlevel for transmitting over the second air interface may be retrievedfrom memory 512. In other embodiments, the maximum available power levelfor transmitting over the second air interface may be calculated as thedifference between a total power available to wireless communicationdevice 500 for transmitting over the first air interface and the secondair interface, and the first power level determined at step 702.

At a next step 706, the differential check unit 506 may determinewhether the maximum available power level for transmitting over thesecond interface differs from the first interface power level fortransmitting over the first interface by at least a power differentialthreshold. If they do not differ by a power differential threshold,process 706 continues to a step 708. At step 708 the second power leveladjuster 508 sets an estimated power level for transmitting over thesecond air interface to the difference between the maximum availablepower level for transmitting over the second interface and the firstinterface power level for transmitting over the first interface. Theprocess then continues to step 712.

If at step 706 it is determined the maximum available power level fortransmitting over the second interface does differ from the firstinterface power level for transmitting over the first interface by atleast a power differential threshold, the process continues to step 710.At step 710 the second power level adjuster 508 sets the estimated powerlevel for transmitting over the second air interface such that thedifference between the estimated power level for transmitting over thesecond air interface and the first interface power level fortransmitting over the first interface does not exceed the powerdifferential threshold. The process then continues to step 712.

At step 712, the power-based payload constraint is calculated. In oneembodiment, the estimated power available for transmitting data trafficover the second air interface is first calculated as the differencebetween: the estimated power level for transmitting over the second airinterface; and the second transmit pilot power adjusted for the overheadgain and the power margin. The power-based payload constraint is thencalculated as the estimated power available for transmitting datatraffic over the second air interface adjusted for the second transmitpilot power and the power margin. The process 700 then continues to step714. At step 714, the processor 512 uses the power-based payloadconstraint to allocate power to the first air interface and the secondair interface. The power-based payload constraint is indicative of thepower level chosen for transmission over the second air interface.Embodiments of power allocation schemes are described below.

In some embodiments, the first air interface is the preferred airinterface. In some such embodiments, the allocation of resources for thefirst air interface may take priority over the second air interface. Forexample, the allocation of power to the first air interface may not belimited. In other words, if the composite of the chosen power levels fortransmission over the first air interface and the second air interfaceexceeds the overall power available, the first air interface will beallocated power before the second air interface is allocated power. Thesecond air interface will be allocated any power that remains after thefirst air interface is allocated power. Therefore, if the chosen powerlevel for the first air interface is X W, the chosen power level for thesecond air interface is Y W, and the overall power available is Z W, thepower is allocated as follows. If X+Y≦Z, then the first air interfacemay be allocated X W, and the second air interface may be allocated Y W.If X+Y>Z and X<Z, then the first air interface may be allocated X W, andthe second air interface may be allocated Z−X W. Further, if X+Y>Z andX≧Z, then the first air interface may be allocated the entire Z Wavailable.

Other priority schemes for allocating resources may be used as well. Forexample, the allocation of power to the first air interface may beprioritized from 0 W to A W. Further, the total transmit power availablemay be Z W. Accordingly, the first air interface is allocated powerbefore the second air interface up to A W. The second air interfaces maythen be allocated power up to Z W—the number of watts used allocated tothe first air interface. Any unallocated power may be used to fulfillthe remaining power allocation, if any, requested by the first airinterface. For example, the chosen power level for the first airinterface may be X W, where X>A. The chosen power level for the secondair interface may be Y W. If X+Y>Z and A+Y>Z, then the first airinterface is allocated A W and the second air interface is allocated Z−AW. If X+Y>Z and A+Y<Z, then the first air interface is allocated Z−Y Wand the second air interface is allocated Y W. If X+Y>Z and X<Z, thenthe first air interface may be allocated X W, and the second airinterface may be allocated Z−X W. One of ordinary skill in the art willrecognize other schemes may be used as well, such as several prioritylevels for allocating power (e.g., the first air interface isprioritized for the first A W, the second air interface for the next BW, the first air interface for the next C W, etc.).

FIG. 8 illustrates a flowchart of a process 800 of adjusting the powermargin using a margin loop. At step 802 it is determined if the secondtransmit pilot power is greater than an upper bound for the transmitpilot power. The upper bound may be predetermined. If it is determinedthe pilot power is greater than the upper bound, process 800 continuesto step 806. If it is determined the pilot power is not greater than theupper bound, process 800 continues to step 804. At step 804 it isdetermined if the composite of the chosen power levels for transmissionover the first air interface and the second air interface exceeds theoverall power available. If it is determined the composite exceeds theoverall power available, the process continues to step 806. If it isdetermined the composite does not exceed the overall power available,the process continues to step 808.

At step 806, the power margin is compared to a maximum power margin. Themaximum power margin may be predetermined. If increasing the powermargin would cause the power margin to exceed the maximum power margin,process 800 continues to step 810 where the power margin is set to themaximum power margin. If it is determined increasing the power marginwould not cause the power margin to exceed the maximum power margin,process 800 continues to step 816, where the power margin is increasedby an amount. In some embodiments, the increase interval ispredetermined.

At step 808, the power margin is compared to a minimum power margin. Theminimum power margin may be predetermined. If decreasing the powermargin would cause the power margin to fall behind the minimum powermargin, process 800 continues to step 812 where the power margin is setto the minimum power margin. If it is determined decreasing the powermargin would not cause the power margin to fall behind the minimum powermargin, process 800 continues to step 814, where the power margin isdecreased by an amount. In some embodiments, the decrease interval ispredetermined. The increase interval, decrease interval, maximum powermargin, and/or minimum power margin may be based on the types of airinterfaces used by the wireless communication device.

While the specification describes particular examples of the presentinvention, those of ordinary skill can devise variations of the presentinvention without departing from the inventive concept. For example, theteachings herein refer to circuit-switched network elements but areequally applicable to packet-switched domain network elements.

Those skilled in the art will understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those skilled in the art will further appreciate that the variousillustrative logical blocks, modules, circuits, methods and algorithmsdescribed in connection with the examples disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,methods and algorithms have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentinvention.

The various illustrative logical blocks, modules, and circuits describedin connection with the examples disclosed herein may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The methods or algorithms described in connection with the examplesdisclosed herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. A storagemedium may be coupled to the processor such that the processor can readinformation from, and write information to, the storage medium. In thealternative, the storage medium may be integral to the processor. Theprocessor and the storage medium may reside in an ASIC.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosed examples is provided to enableany person skilled in the art to make or use the present invention.Various modifications to these examples will be readily apparent tothose skilled in the art, and the generic principles defined herein maybe applied to other examples without departing from the spirit or scopeof the invention. Thus, the present invention is not intended to belimited to the examples shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for allocating power among multiple airinterfaces for a communication device supporting simultaneoustransmission over multiple air interfaces, the method comprising:determining a first power level that is used for transmitting over afirst air interface; determining an available power level fortransmitting over a second air interface; comparing a difference betweenthe available power level and the first power level to a powerdifferential threshold; setting a second power level for transmittingover the second air interface to the available power level in responseto a determination that the difference between the available power leveland the first power level fails to exceed the power differentialthreshold; setting the second power level for transmitting over thesecond air interface to an adjusted power level in response to adetermination that the difference between the available power level andthe first power level exceeds the power differential threshold, whereina difference between the adjusted power level and the first power levelfails to exceed the power differential threshold; and generating apower-based payload constraint based on at least the second power level.2. The method of claim 1, further comprising allocating power to thefirst air interface and to the second air interface based on thepower-based payload constraint.
 3. The method of claim 2, wherein thepower allocated to the first air interface is prioritized over the powerallocated to the second air interface.
 4. The method of claim 2, whereinthe power allocated to the first air interface is prioritized over thepower allocated to the second air interface up to a priority powerlevel, and wherein the power allocated to the second air interface isprioritized over the power allocated to the first air interface from arange between the priority power level and a total available power. 5.The method of claim 4, wherein the total available power corresponds toa sum of the first power level and the available power level.
 6. Themethod of claim 1, wherein generating the power-based payload constraintis further based on a power margin, an overhead gain, and a transmitpilot power for transmitting a pilot over the second air interface. 7.The method of claim 1, further comprising adjusting a power margin basedon a transmit pilot power.
 8. The method of claim 7, further comprisingadjusting the power margin based on a total transmit power.
 9. Awireless communication device supporting simultaneous transmission overmultiple air interfaces, the wireless communication device comprising: afirst interface power level calculator configured to determine a firstpower level that is used for transmitting over a first air interface; asecond interface power level calculator configured to determine anavailable power level for transmitting over a second air interface; adifferential check unit configured to compare a difference between theavailable power level and the first power level to a power differentialthreshold; a second interface power level adjuster configured to: set asecond power level for transmitting over the second air interface to theavailable power level in response to a determination that the differencebetween the available power level and the first power level fails toexceed the power differential threshold; and set the second power levelfor transmitting over the second air interface to an adjusted powerlevel in response to a determination that the difference between theavailable power level and the first power level exceeds the powerdifferential threshold, wherein a difference between the adjusted powerlevel and the first power level fails to exceed the power differentialthreshold; and a power-based payload constraint calculator configured togenerate a power-based payload constraint based on at least theestimated second power level.
 10. The device of claim 9, furthercomprising a power controller configured to allocate power to the firstair interface and to the second air interface based on the power-basedpayload constraint.
 11. The device of claim 10, wherein the powerallocated to the first air interface is prioritized over the powerallocated to the second air interface.
 12. The device of claim 10,wherein the power allocated to the first air interface is prioritizedover the power allocated to the second air interface up to a prioritypower level, and wherein the power allocated to the second air interfaceis prioritized over the power allocated to the first air interface froma range between the priority power level and a total available power.13. The device of claim 12, wherein the total available powercorresponds to a sum of the first power level and the available powerlevel.
 14. The device of claim 9, wherein the power-based payloadconstraint calculator is further configured to generate the power-basedpayload constraint based on a power margin, an overhead gain, and atransmit pilot power for transmitting a pilot over the second airinterface.
 15. The device of claim 9, further comprising a processorconfigured to adjust a power margin based on a transmit pilot power. 16.The device of claim 15, further comprising a processor configured toadjust the power margin based on a total transmit power.
 17. A systemfor allocating power among multiple air interfaces for a communicationdevice supporting simultaneous transmission over multiple airinterfaces, the system comprising: means for determining a first powerlevel that is used for transmitting over a first air interface; meansfor determining an available power level for transmitting over a secondair interface; means for comparing a difference between the availablepower level and the first power level to a power differential threshold;means for setting a second power level for transmitting over the secondair interface, wherein the second power level is set to the availablepower level in response to a determination that the difference betweenthe available power level and the first power level fails to exceed thepower differential threshold, wherein the second power level is set toan adjusted power level in response to a determination that thedifference between the available power level and the first power levelexceeds the power differential threshold, and wherein a differencebetween the adjusted power level and the first power level fails toexceed the power differential threshold; and means for generating apower-based payload constraint based on at least the estimated secondpower level.
 18. The system of claim 17, further comprising means forallocating power to the first air interface and to the second airinterface based on the power-based payload constraint.
 19. The system ofclaim 18, wherein the power allocated to the first air interface isprioritized over the power allocated to the second air interface. 20.The system of claim 18, wherein the power allocated to the first airinterface is prioritized over the power allocated to the second airinterface up to a priority power level, and wherein the power allocatedto the second air interface is prioritized over the power allocated tothe first air interface from a range between the priority power leveland a total available power.
 21. The system of claim 20, wherein thetotal available power corresponds to a sum of the first power level andthe available power level.
 22. The system of claim 17, wherein the meansfor generating the power-based payload constraint is further configuredto generate the power-based payload constraint based on a power margin,an overhead gain, and a transmit pilot power for transmitting a pilotover the second air interface.
 23. The system of claim 17, furthercomprising means for adjusting a power margin based on a transmit pilotpower.
 24. The system of claim 23, further comprising means foradjusting the power margin based on a total transmit power.
 25. Acomputer-readable storage device comprising: code for causing a computerto determine a first power level that is used for transmitting over afirst air interface; code for causing the computer to determine anavailable power level for transmitting over a second air interface; codefor causing the computer to compare a difference between the availablepower level and the first power level to a power differential threshold;code for causing the computer to set a second power level fortransmitting over the second air interface to the available power levelin response to a determination that the difference between the availablepower level and the first power level fails to exceed the powerdifferential threshold; code for causing the computer to set the secondpower level for transmitting over the second air interface to anadjusted power level in response to a determination that the differencebetween the available power level and the first power level exceeds thepower differential threshold, wherein a difference between the adjustedpower level and the first power level fails to exceed the powerdifferential threshold; and code for causing the computer to generate apower-based payload constraint based on at least the second power level.